The production of semiconductor products, such as integrated circuits, involves the processing of wafers in a wafer processing system. A plasma processing system is a type of wafer processing machine that employs one or more processing chambers to selectively etch materials from and deposit materials on wafers. To facilitate wafer transport between the atmospheric environment and the more controlled environments within the various processing chambers, load locks are often employed. Wafers are transported by robot arms and positioned on a set of holders, or fingers, in the load lock.
It is possible that in some cases, a wafer among a stack of wafers in the load lock may be incorrectly placed in a slot, or may slip off one of the fingers and falls on a wafer below, or may be missing from a slot, or a wafer may be present in a slot that should not have any wafer in it. In these cases, it is desirable to rapidly acquire wafer physical placement data and to detect abnormalities so that remedial actions may be taken (such as opening to load lock to retrieve the incorrectly positioned wafer) before damage to the wafer and/or to wafer transport sub-assemblies may occur.
Laser micrometers have often been employed for the purpose of determining the aggregate percentage of light in a CCD array that is blocked by a particular object. However, laser micrometers are not well suited for efficiently determining the actual physical locations of multiple discrete objects in their assigned locations as well as the individual physical location data regarding where these objects are located.
In other production or research environments, it is sometimes desirable to rapidly acquire and analyze data regarding the actual physical placement of multiple discrete objects relative to their assigned positions. The present disclosure relates to low-cost, highly efficiency apparatuses and methods for acquiring the actual physical placement data for multiple discrete objects and to efficiently analyze the actual physical placement data with respect to their assigned or expected positions.